With the rapid widespread use of computers and the start-up of digital broadcasting or the like, there have been demands for a hard disk drive with a larger storage capacity. To increase the storage capacity, e.g., the recording area is increased by suppressing the occurrence of roll-off (edge rounding of the end side of a substrate) during the polishing process of a memory hard disk used in a hard disk drive. As a polishing composition for suppressing roll-off, e.g., JP 2002-167575 A proposes a polishing composition including a monomer compound of polyoxyethylene and an acid, and JP 2003-160781 A proposes a polishing composition including a monomer compound such as polyoxyethylene sorbitan fatty acid ester.
However, as the information society expands, a further increase in the storage capacity is required. Therefore, the effect of suppressing roll-off by the conventional polishing compositions is not sufficient to meet such a requirement, and a polishing composition capable of suppressing more roll-off has been needed.